Interpretive Summary: Ergot alkaloids have been implicated in causing constriction of blood vessels, which is a source of symptoms of the fescue toxicosis syndrome. This syndrome is a problem for grazing animals that use foregut or rumen fermentation to meet the majority of their dietary needs. The objective of this study was to determine if these alkaloids have the potential to cause bovine ruminal artery and vein to contract. Results presented in this study show that ergot alkaloids do indeed have the potential to induce a contractile response in bovine right ruminal artery and vein preparations. This could alter blood flow to the rumen and have a negative impact on absorption of nutrients. Constriction of ruminal arteries and veins could be another contributing source of the reduced performance observed in cattle grazing tall fescue pastures infected with the ergot alkaloidproducing fungus.

Technical Abstract:
Alkaloids produced by the Neotyphodium coenophialum endophyte associated with tall fescue (Lolium arundinaceum) are imputed to cause symptoms of fescue toxicosis related to peripheral vasoconstriction. These compounds were hypothesized to correspondingly affect foregut vasculature. The objective of this study was to determine vasoconstrictive potentials of ergovaline, ergotamine, ergocryptine, ergocristine, ergonovine, ergocornine, and lysergic acid on right ruminal artery and vein. Segments of right ruminal artery and vein were collected from the ventral coronary groove of predominately Angus heifers (n = 10) shortly after slaughter and placed in a modified Krebs-Henseleit buffer on ice. Vessels were cleaned of excess connective tissue and fat, sliced into 2-3 mm segments and suspended in a multi-myograph chamber with 5 mL of continuously oxygenated Krebs-Henseleit buffer (95 %O2/5% CO2; pH 7.4; 37°C). Arteries and veins were equilibrated to 1.0 g and 0.5 g respectively for 90 min followed by the reference addition of 120 mM KCl. Increasing concentrations of each alkaloid were added to the respective chamber every 15 min following buffer replacement. Data were normalized as a % of the contractile response induced by KCl. Alkaloid, concentration, and vessel affected contractility (P < 0.05). No arterial response was observed until 1×10-6 M for ergovaline and ergotamine, 1×10-5 M for ergocryptine, ergocornine, and ergonovine, and 1×10-4 M for ergocristine. Lysergic acid did not induce a significant contractile response in the ruminal artery. A venous contractile response was not observed until 1×10-6 M for ergovaline, 1×10-5 M for ergotamine, and 1×10-4 M for ergocryptine and ergocristine. Lysergic acid, ergonovine, and ergocornine did not induce a significant contractile response in the ruminal vein. A greater arterial maximal response was observed for ergovaline (P < 0.05), whereas the arterial and venous responses were not different for ergotamine, ergocryptine, and ergocristine (P > 0.05). These results indicate that ergot alkaloids isolated from the tall fescue – endophyte symbiont have potential to alter blood supply and drainage from the bovine foregut.